.22 isn’t even a great caliber for accuracy. .22lr is great for accuracy. Given that this bullet bounced off, I’d wager it was just a .22 short.
It was apparently old ammo that had lost some of it's potency.
However, this isn't the first time I've heard of .22 rounds not penetrating the front of an assailant's skull.
A .22 is still better than nothing, but it would seem wise to use the most potent .22 round that you can.
Some older people have problems with their hands that dictate not using a larger caliber or heavier gun, so while a .22 isn't ideal, it still is a reasonable choice for some.
I bet your right.
We punch holes through plywood regulary at 50 yards with .22 LR.